Hello Naveen,
in GSR and ASR forwarding is hardware based, they are not software based routers like ISR and ISR G2, they are more similar to multi layer switch in this aspect.
GSR and CRS run IOS XR and are backbone routers for SP networks ( P/PE role). They are totally distributed nodes
ASR 9000 run IOS XR and are specialized on metro ethernet and carrier ethernet ( PE role for Metro ethernet/ carrier ethernet) in SP networks. Also this should be distributed node.
ASR 1000 runs IOS XE and have a route processor and a forwarding processor ( ESP). They can be PE or Aggregation routers at the edge ( for example IPSecVPN concentrator)
for more details
http://www.cisco.com/en/US/products/hw/routers/index.html
Hope to help
Giuseppe
